The present invention relates to a method of producing an optofibre cable and an optofibre cable produced in accordance with the method, and then particularly an optofibre cable for transmitting optosignals and comprising a plurality of optofibres housed in tubular elements or pipes enclosed by a protective sheath.
It is known in several different contexts to use optofibre cables that include optofibre-containing plastic tubular elements that are wound around and joined to a strain relief and enclosed in a protective sheath. The tubular element interspacing is filled with a filling material so as to fixate the tubular elements in the cable and to make the cable watertight along its length.
The problem with this type of optocable is that capillaries are liable to form between the filling material and the plastic tubular elements, therewith making it possible for water to enter the cable along its length. The filling material also tends to make the cable much too heavy and inflexible.
With the intention of simplifying the manufacture and handling of optofibre cables and also with the intention of preventing the ingress of water into optofibre cables connected to components, there has been produced an optofibre cable which includes one or more tubular elements that house one or more optofibres, a central strain relief connected to said tubular elements, and an intermediate porous filling material, all of which are enclosed in a protective casing in the form of a conduit means. The optofibre-containing tubular elements are glued to the strain relief. The purpose of the porous filling material is to fill the space between the tubular elements, the glue surface on the strain relief and the casing and to fixate the tubular elements around said strain relief, while still enabling the propagation of the glue connection and the function of said glue connection in making the optofibre cable watertight along its length. The use of a porous filling material means that less material is used than in known cases and therewith results in a cable of lower weight. Despite being porous, the filling material is still able to assist in mutual fixation of the plastic tubular elements in the cable and will render the cable shape-stable and watertight along its length. The glue join between the strain relief and the plastic tubular elements can be made stronger, by applying a thicker layer of glue so as to increase the contact surface area between plastic tubular elements and glue layer, therewith obtaining better adhesion and improved connection of the plastic tubular elements with the strain relief. The risk of the formation of capillaries between the plastic tubular elements, the glue layer and the filling material is also reduced with this thicker glue layer, therewith avoiding the risk of water leaking into the cable along its length. In addition to making the glue layer thicker on the strain relief, an increased use of glue will enable the plastic tubular elements to be provided with an outer glue layer instead of an outer plastic mantle, therewith enabling one or more arrays of plastic tubular elements with intermediate porous filling material to be arranged and the whole embraced by an outer protective casing, such as a plastic sheath.
The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawing.